Thermodynamics of diffusive DM/DE systems

Abstract

We discuss the energy density,temperature and entropy of dark matter (DM) and dark energy (DE) as functions of the scale factor $a$ in an expanding universe. In a model of non-interacting dark components we repeat a derivation from thermodynamics of the well-known relations between the energy density,entropy and temperature. In particular, the entropy is constant as a consequence of the energy conservation. We consider a model of the DM/DE interaction where DM energy density increase is proportional to the particle density. In such a model the dependence of the energy density and the temperature on the scale factor $a$ is substantially modified. We discuss (as a realization of the model) DM which consists of relativistic particles diffusing in an environment of DE. The energy gained by the dark matter comes from a cosmological fluid with a negative pressure. We define the entropy and free energy of such a non-equilibrium system. We show that during the universe evolution the entropy of DM is increasing whereas the entropy of DE is decreasing. The total entropy can increase (in spite of the energy conservation) as DM and DE temperatures are different. We discuss non-equilibrium thermodynamics on the basis of the notion of relative entropy.

arXiv comment20 pages

References in corpus (20)

• Dynamics of dark energy with a coupling to dark matter
• Cosmological Evolution With Interaction Between Dark Energy And Dark Matter
• Le Chatelier-Braun principle in cosmological physics
• A Larger Estimate of the Entropy of the Universe
• Thermodynamics of Decaying Vacuum Cosmologies
• A thermodynamic motivation for dark energy
• Gravitationally Induced Particle Production: Thermodynamics and Kinetic Theory
• Can Dark Matter Decay in Dark Energy?
• The generalized second law of gravitational thermodynamics on the apparent and event horizons in FRW cosmology
• Temperature Evolution Law of Imperfect Relativistic Fluids
• Entropy of gas and dark matter in galaxy clusters
• Relativistic diffusion
• Diffusion in an expanding medium: Fokker-Planck equation, Green's function and first-passage properties
• Dynamics of the diffusive DM-DE interaction--dynamical system approach
• General treatment for dark energy thermodynamics
• Relativistic diffusion with friction on a pseudoriemannian manifold
• Does the diffusion DM-DE interaction model solve cosmological puzzles?
• Energy and entropy of relativistic diffusing particles
• Einstein gravity of a diffusing fluid
• A relation between diffusion,temperature and the cosmological constant

Cited by in corpus (5)

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• Modeling the Past Hypothesis: A Mechanical Cosmology
• Spacetime symmetries and geometric diffusion